1. Field of the Invention
This invention relates to methods and apparatus for supplying power to a load circuit from main and alternate electric power sources.
2. Description of Related Art
Increasing numbers of critical appliances or devices such as computers, alarm systems or heating/cooling systems are being employed in commercial buildings and residences. Many of these appliances and/or devices require a continuous supply of electrical power. Most residential and commercial buildings are wired for AC electric power supplied only from a single utility electric power source. In some areas this utility electric power source can be unreliable or expensive. Consequently, it is desirable to be able to use alternate sources of electric power as backup electric power sources to ensure a continuous supply of electric power or as less expensive electric power sources.
Commonly, alternate electric power sources such as generators and inverters, for example, are wired to separate circuits and separate outlets or are used as alternate electric power sources to a conventional AC electric power distribution panel normally supplied with electrical power from an electric power utility. Connecting individual appliances to separate circuits or separate outlets is impractical, as a user would have to connect each appliance to an appropriate outlet to receive electric power from either the main electric power source or the alternate electric power source, as required. Many generators, for example, have built in AC receptacles by which they supply electric power but they can only accommodate a few appliances or devices at best.
Alternatively, individual devices or appliances can be wired directly to a separate electric power distribution system which may be connected to a transfer mechanism operable to receive electric power from first and second AC electric power sources. This is often done where critical load circuits are to be backed up by an alternate AC electric power source. These load circuits are usually removed from the main electrical panel and wired into a secondary sub-panel. This sub-panel is then powered through a manual transfer switch or automatic transfer switch for controlling electric power supplied to the entire secondary panel. When AC electric power failure occurs from the first source only those devices wired to the separate electric power distribution system are operable to draw electric power from the second AC electric power source. The main disadvantage of this system is that every device or appliance needing backup electric power must be wired to this special, separate electric power distribution system, which may require substantial re-wiring of circuits throughout a building. This has the additional disadvantage of limiting the locations the devices or appliances can be placed, and necessitates circuit rewiring when devices or appliances are moved. In addition, alternately sourcing an AC electric power distribution panel with an alternate source requires the ability to switch large currents which mandates the use of expensive high current switching equipment. Since commercial buildings are often renovated for new tenants, re-wiring for back-up of critical loads and providing an alternate electric power source could quickly become cost prohibitive. This can be a cost prohibitive barrier to market entry for back-up electric power alternative energy products.
In addition, there is currently no device which manages loads by controlling access to separate electric power feeds. Such a device could be useful in controlling energy costs where a user may select an electric power source based on the most economical rates.
What would be desirable therefore is a simple way of supplying certain load circuits normally supplied by an AC electric power distribution panel, with separate sources, in the event that AC electric power failure of the main source occurs or in the event that it is desired to supply a particular local circuit with an alternate source of electric power.
The above problems are addressed by providing a method for supplying power to a load circuit from main and alternate electric power sources. The method involves actuating a signal-controlled selector inside a housing, at least a portion of which is received in a breaker receptacle of an electric power distribution panel such that a first conductor on the housing is operable to receive electric power from the electric power distribution panel and a second conductor on the housing is operable to receive electric power from an alternate electric power source, to selectively connect the load circuit to the first conductor or to the second conductor, in response to a control signal.
The method may include causing relative movement between at least one of a transfer contact, a supply contact connected to the first conductor, and an alternate contact connected to the second conductor. This may include moving a plunger in communication with at least one of the transfer contact, the supply contact, and the alternate contact, which may further include imposing a magnetic force on the plunger. The method may also include producing a control signal and producing a magnetic force in response to the control signal. This may involve energizing a solenoid coil operable to produce the magnetic force on the plunger.
The method may also include protecting the load circuit from overload current, and may further include preventing current from being supplied to the load circuit when overload current is supplied to the load from either the panel or the alternate source. This may involve actuating a mechanism when the overload current is supplied to the load circuit, and separating contacts through which current is supplied to the load circuit in response to actuation of the mechanism.
The method may also include arming the mechanism in response to actuation of an exterior portion of an actuator of the mechanism extending outside of the housing, and engaging the contacts through which current is supplied to the load circuit in response to arming of the mechanism.
In accordance with another aspect of the invention there is provided an apparatus for supplying power to a load circuit from main and alternate electric power sources. The apparatus includes a housing having a first conductor thereon, at least a portion of the housing being receivable in a breaker receptacle to facilitate receipt of power from the main electric power source at the first conductor, a second conductor on the housing operable to receive electric power from an alternate electric power source, and means for selectively connecting the load circuit to the first conductor or to the second conductor, in response to a control signal.
The apparatus may include a transfer contact, a supply contact connected to the first conductor and an alternate contact connected to the second conductor and means for causing relative movement between at least one of the transfer contact, the supply contact and the alternate contact.
The apparatus may also include a plunger and means for moving the plunger into communication with at least one of the transfer contact, the supply contact and the alternate contact. The means for moving the plunger may include means for imposing a magnetic force on the plunger which may include a solenoid coil operable to be powered by the main electric power source.
The apparatus may further include protection means for protecting the load circuit from overload current, which may also include means for preventing current from being supplied to the load circuit when an overload current is supplied to the load circuit from either the main electric power source or the alternate electric power source.
The apparatus may further include an armable mechanism and means for actuating the mechanism when an overload current is supplied to the load circuit. The mechanism may be operable to positively separate contacts through which current is supplied to the load circuit in response to actuation of the mechanism. Means for arming the mechanism may also be included, which may include an actuator having an exterior portion extending outside of the housing. The mechanism may be operable to engage the contacts through which current is supplied to the load circuit in response to arming of the mechanism.
In accordance with another aspect of the invention, there is provided an apparatus for supplying power to a load circuit from a main electric power source or an alternate electric power source. The apparatus includes a housing having a first conductor thereon, at least a portion of the housing being receivable in a breaker receptacle to facilitate receipt of power from the main electric power source at the first conductor, a second conductor on the housing operable to receive electric power from an alternate electric power source, and a signal-controlled selector operable to connect the first conductor or the second conductor to the load circuit in response to a control signal.
The signal-controlled selector may include a selector contact arrangement, the first and second conductors being connected to the selector contact arrangement. The selector contact arrangement may further include a main contact operable to receive power from the first conductor, an alternate contact operable to receive power from the alternate source, and a transfer contact operable to be selectively connected to the main contact or the alternate contact.
The apparatus may further include a device operable to move the transfer contact between the supply contact and the alternate contact. The device may include a solenoid and a plunger movable in response to a magnetic force produced by the solenoid. The solenoid may be operable to receive power from the first conductor such that the solenoid can be energized by power from the main electric power source and de-energized when power is not available from the main electric power source.
The apparatus may also include a control operable to prevent movement of the plunger, and the control may include an interference member operable to interfere with movement of the plunger. An interference actuator may be included which is accessible from outside the housing and operable to cause the interference member to interfere with movement of the plunger.
The apparatus may further include an alternate source protector for protecting the load circuit from overload currents from the alternate source. The alternate source protector may include a positioner operable to position the alternate source contact in proximity with or away from the transfer contact. The positioner may include a movable member on which the alternate contact is situate, and a support for supporting the movable member in proximity with the transfer contact such that the transfer contact and the alternate contact can be engaged. The positioner may further include a spring for biasing the movable member away from the transfer contact.
The alternate source protector may include a current sensitive device operable to move the support away from the movable member, to permit the movable member to move away from the transfer contact such that the transfer contact is not able to engage the alternate contact. The current sensitive device may include a bimetallic member.
The apparatus may also include a main source protector for protecting the load circuit from overload current when the load circuit is being supplied with power from the main electric power source. The main source protector may include a main protection contact and a main inlet contact, at least one of which is movable relative to the other, and may further include a second current sensitive element operable to move the at least one of the main protection contact and the main inlet contact away from each other in response to overload current through the main protection contact.
The apparatus may also include a flexible main protection conductor supporting the main protection contact and a second heat sensitive element on the flexible main conductor arranged to cause the flexible main protection conductor to bend to effect movement of the main protection contact away from the main inlet contact.
A main source protector and an alternate source protector for protecting the load circuit from overload current may both be included in the apparatus. The apparatus may also include an actuator and an armable mechanism in communication with the alternate source protector and the main source protector, the actuator having an interior portion inside the housing and an exterior portion extending outside the housing, the exterior portion facilitating arming of the mechanism by movement of the exterior portion, the mechanism being disarmed by operation of either of the alternate source protector and the main source protector. The mechanism may be operable to open a set of contacts to prevent current from being supplied to the load from the main electric power source or from the alternate electric power source. Actuation of the actuator to arm the mechanism may be operable to engage the set of contacts to permit current to be supplied to the load from either the main electric power source or the alternate electric power source.
The apparatus may further include a signal generator for generating the control signal for controlling the signal-controlled selector, and may also include a main source protector for protecting the load circuit from overload current when the load circuit is being supplied with power from the main electric power source. The main source protector may include a main protection contact and a main inlet contact, at least one of which is movable relative to the other, and a second current sensitive element operable to move the at least one of the main protection contact and the main inlet contact away from each other in response to excessive current through the main protection contact. In addition, the apparatus may include a flexible main protection conductor supporting the main protection contact and a second heat sensitive element on the flexible main conductor arranged to cause the flexible main protection conductor to bend to effect movement of the main protection contact away from the main inlet contact.
The apparatus may also include an actuator and an armable mechanism in communication with the alternate source protector and the main source protector, the actuator having an interior portion inside the housing and an exterior portion extending outside the housing, the exterior portion facilitating arming of the mechanism by movement of the exterior portion.
In addition, the apparatus may include a first member connecting the actuator to the first current sensitive element such that movement of the first current sensitive element imparts movement to the actuator to disarm the mechanism, and a second member connecting the actuator to the second current sensitive element such that movement of the second current sensitive element imparts movement to the actuator to disarm the mechanism. The movement of the actuator which arms the mechanism may be operable to simultaneously engage the first protection contact with the alternate supply contact and to simultaneously engage the inlet contact with the main protection contact. Movement of the actuator which disarms arms the mechanism may be operable to disengage the first protection contact with the alternate supply contact and to disengage the inlet contact with the alternate protection contact.
Through use of the embodiments of the invention described herein, the need to rewire panels in existing buildings to supply circuits with alternate sources of electric power is removed. In addition, the need for a secondary sub-panel in new construction is removed. Furthermore, use of such embodiments provides for safer installation by having only one place within a given building to disconnect a load from AC electric power and by ensuring that backfeed of electric power into the utility or into the alternate source cannot occur.
Use of such embodiments of the invention also provides a competitive advantage in that rewiring an existing panel is no longer required. The cost of rewiring as compared to the cost of use of the modules described herein can be as high as 50 to 1, depending upon the access to the existing main AC electric power distribution panel.
Finally, in conventional high current systems which provide for switching of an electric power distribution panel feed from a conventional high current AC source to an alternate current source, transfer speeds are relatively slow because of the large ampere ratings of the relays required to be actuated. Furthermore, the distance required between contacts of this type of transfer device increases proportionately to the current carrying capacity. Even sub-panel transfer relays are relatively large and very slow, making them impractical for computers and process control equipment. Using the embodiments of the invention provided herein, transfer occurs at the load circuit level and therefore switching is done on currents of lesser magnitude which enables smaller components to be used, such smaller components having less mass and requiring less spacing than higher current apparatus, resulting in faster transfer speeds, rendering embodiments of the invention more suitable for use with computers and process control equipment.
Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.